The present invention relates to an image forming apparatus detachably provided with a cartridge to which process materials for image formation such as an image carrier and the like, are integrally assembled.
As an apparatus in which a color image can be obtained by an electrophotographic method, there is the following apparatus in which: latent image formation according to a number of separated colors of a document image and development by color toners are repeatedly conducted on a photoreceptor drum or photoreceptor belt; color toner images are superimposed on the photoreceptor drum or the photoreceptor belt; and after that, they are transferred so that a color image can be obtained. A basic process of the multi-color image formation is disclosed in Japanese Patent Publication Open to Public Inspection Nos. 75850/1985, 76766/1985, 95456/1985, 95458/1985, and 158475/1985, by the inventors of the present invention.
In a multi-color image forming apparatus in which a color image can be obtained by the aforementioned superimposition, a plurality of developing units, in which different color toners are contained, are provided around the photoreceptor, and generally the photoreceptor is rotated by plural turns so that latent images can be developed, and after that, a color image can be obtained on a transfer paper by a transfer unit which is provided opposite to a peripheral surface of the photoreceptor.
With respect to the aforementioned image forming apparatus, the apparatus having the following structure has been proposed. That is, some of the image forming means are provided in the form of a cartridge for supply or replacement when the photoreceptor, developer carrier, a cleaning member or developer toner, the lives of which are limited, are consumed, and a member into which a main section of the image forming means is integrated is removed from the apparatus so that maintenance or replacement can be conducted. Further, a structure in which a conveyance path of a transfer material on which an image is formed by an image forming means, is accessible so that the transfer material can be easily removed when jamming occurs, has been proposed.
Furthermore, in the image forming apparatus of a digital type, a laser writing system is used as a latent image forming means on the photoreceptor, and in many cases, the laser writing system is detachably provided in the form of a unit, the same as the aforementioned process cartridge, so that cleaning and inspection can be conducted easily.
As for the process cartridge of the aforementioned image forming apparatus, it is necessary that the process cartridge is automatically connected with or detached from a driving means provided in the apparatus main body. Usually, a method by which the process cartridge is detachably connected with the drive means through a gear, is applied as the means required above. However, in power transmission through the gear, accurate and smooth transmission of rotation speed is difficult due to delicate variations of engagement between teeth of gears, or high frequency noises from peripheral units to a motor as a driving source, and slight fluctuations of the rotation can be generated, and thereby, sometimes, image quality can be lowered, especially with regard to the photoreceptor.
For the purpose of making up the disadvantages in power transmission through the gears, the following method has been proposed in which: a flywheel is provided on a rotation shaft of the photoreceptor so that the photoreceptor can be smoothly rotated. However, as is commonly known, the photoreceptor is rotated at a relatively low speed, and therefore, a large effect of inertia can not be obtained. Further, when the flywheel is provided, there are disadvantages in which: volume and weight of the process cartridge is increased, and thereby operability is lowered.